<!doctype html>
<html>
    <head>
        <style>
            .container {
                width: 400px;
                background: #ddd;
            }
            .text-input {
                width: 50%; /* 200px */
                padding: 10%; /* 40px */
                background: #fff;
            }
        </style>
    </head>
    <body>
        <div class="container">
            <input type="text" class="text-input" />
        </div>
    </body>
</html>
